Natural action is sequentially coordinated. It is characterized by complex and pervasive patterns or rules, which organize the connections of elemental movements into effective behavioral sequences. Implementation of such patterning rules by the brain is crucial to normal behavior. When damage to striatal or related brain structures involved in sequential patterning and in high level sensorimotor integration occurs in human Huntington's or Parkinson's disease, enormous behavioral disruption results. Equivalent disruption in the patterning of natural behavior in animals can be produced by analogous brain damage. This proposal uses patterns of natural species-specific action structure to examine how striatal circuits carry out their behavioral sequencing and high-level integration functions. in particular, these experiments will: a) specify striatal subregions and neurotransmitter systems crucial to natural sequencing and sensorimotor function, b) identify the role of sensory-to-motor linkage modulation in the striatal control of behavioral sequencing, and c) examine the gating role of motivational factors in the control of a choreic sensorimotor pathology that is produced by striatopallidal lesions.